Which Holley manifold?............it's been a long time since aftermarkets did not utilize both bolt patterns. In th emean time, without looking at the carb and doing a "hands on" feel for it, I would suggest dropping the float level and make sure the squirter (accel pump) is still getting adequate fuel to give a decent shot at picking up fuel in it's resevoir for proper "shooting". It's not hard to achieve but with a little bit of perseverence, it is not hard, maybe 4-5 minutes of leaning over the grill and tightening your gut muscles. This is not writen in stone, but start the idle mixture screws at 3-1/2 turns from base and tune accordingly (but slowly backing them out. I have a feeling you'll be replacing this carb, but for now you can make this work. One little bugaboo these things have is the gaskets used can somrtimes have extra holes drilled for vacuum use (accessories,etc) and give bad readings to the fuel demand. Please double check power piston travel for smooth operation (the brass piston that holds primary rods). Any other questions, Let me know. There are combinations for primary rod/jet sizes than can really give you a mild headache.